Guest Editorial
Electric propulsion (EP) has become a key enabling technology for a wide range of space missions, including orbit raising and station keeping, deep-space exploration, and emerging applications such as very-low Earth orbit (VLEO) platforms and small satellite constellations. As EP concepts continue to diversify in terms of physical principles, propellants, and operating regimes, numerical simulation has assumed a central role in supporting design, interpretation of experiments, and system-level optimization.
The Special Issue “Numerical Simulations in Electric Propulsion” was launched with the aim of showcasing recent developments in modeling approaches capable of addressing the multi-physics and multi-scale nature of electric propulsion devices. The contributions collected in this issue reflect the diversity of numerical tools currently employed in the field, ranging from reduced-order plasma models to fluid, kinetic, and hybrid simulations, as well as electromagnetic simulations and system- and mission-level numerical analyses [1,2,3,4,5,6,7,8].
Several papers focus on reduced-order and global plasma modeling, which remain essential for preliminary design phases and for gaining physical insight into complex discharge processes [1,4]. Such models offer a computationally efficient means of exploring large parameter spaces and identifying dominant trends, particularly for novel or less mature concepts, including cathode-less and atmosphere-breathing electric propulsion systems, where plasma chemistry and operating conditions may vary substantially [1,3].
Issues related to plasma stability and unsteady phenomena are also addressed. Numerical investigations of discharge oscillations and instability mechanisms, such as breathing modes in Hall thrusters, contribute to a better understanding of performance limitations and operational constraints [4]. These studies highlight the importance of modeling not only steady-state behavior but also time-dependent dynamics that affect efficiency, lifetime, and interaction with power processing units.
A prominent theme emerging from this Special Issue is the development of multi-regime and multi-fidelity simulation strategies. Electric propulsion devices naturally involve distinct physical regimes, from dense, collisional plasmas in the source region to rarefied, collisionless flows in expansion and plume regions. Contributions dedicated to coupling fluid and Particle-In-Cell (PIC) approaches demonstrate promising pathways toward self-consistent modeling across these regimes, improving predictive accuracy while maintaining manageable computational costs [5].
Advances in the numerical modeling of radio-frequency and helicon-based plasma sources are also represented, with particular attention given to antenna design and wave–plasma coupling. Rational design methodologies supported by full-wave simulations provide practical tools for dimensioning key components and for improving RF power coupling efficiency, with relevance extending beyond propulsion to other high-density plasma applications [6].
Recognizing that propulsion performance cannot be decoupled from subsystem interactions, some contributions address power processing and propellant management through numerical analysis. Models of pulsed plasma thrusters incorporating power electronics considerations illustrate the value of integrated approaches [2], while detailed simulations of xenon handling, such as two-phase flows, flashing phenomena, and tank filling under different gravity conditions, underscore the importance of accurate fluid and thermal modeling for both ground operations and future on-orbit refueling scenarios [7,8].
Finally, the scope of numerical simulations in electric propulsion extends to system- and mission-level considerations. Analyses linking propulsion characteristics to orbital dynamics, particularly in the context of air-breathing electric propulsion and VLEO missions, demonstrate how numerical tools can be used to assess feasibility, define operational envelopes, and support control strategy development under stringent drag and energy constraints [3].
Overall, the contributions gathered in this Special Issue illustrate how numerical simulations serve as a unifying framework across electric propulsion research, connecting plasma physics, device design, subsystem integration, and mission analysis. The Guest Editors would like to thank all authors for the quality and diversity of their contributions, as well as the reviewers for their careful and constructive evaluations. We also acknowledge the support of the Aerospace editorial team throughout the preparation of this Special Issue.
The strong response from the community and the breadth of high-quality contributions clearly demonstrate the success of this Special Issue in capturing current trends and challenges in numerical simulations for electric propulsion, and in fostering cross-fertilization between modeling approaches and propulsion concepts.
Conflicts of Interest
The authors declare no conflict of interest.
References
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